It is known that packaging machines for food products must have high levels of flexibility, performance, sturdiness and reliability so as to be versatile and able to produce a wide variety of different types of packaging.
The vertical packaging machines used in the food sector are mainly those employed in the fruit and vegetable, bakery and confectionery sectors, and make it possible to obtain cushion-type vertical packs, packs with a square base or with several seals.
The dimensions and formats of the bags can vary according to the features of the product to be packaged, the weight of each pack and the different pack formats required.
Packaging machines for food products, above all those with a forming tube, generally consist of a vertical infeed unit comprising a tubular element over which a plastic, PVC or similar material film is fed and through which the pre-dosed product to be packaged is progressively fed.
The plastic, PVC or similar material film is fed over the outside of the forming tube thanks to the use of infeed belts or rollers and is sealed by forming longitudinal and transverse closures thanks to heat-sealing units that can seal and cut the film to size so that the closure of the discharged bag consecutively forms the base of the next bag.
The head cut and seal are achieved with rotating grippers or with “long dwell” or “box motion” type systems.
The longitudinal seal uses drive belts and sealing units to keep the film taut, to seal it and to fold the longitudinal fin.
All the main drives have controlled axes and are connected together in the on-board cabinet thus ensuring maximum expandability of the control system when the machine is equipped with highly complex infeed systems or various devices.
In intermittent functioning machines, the bags are formed with the following operations:                unwinding of the film;        forming of the bag;        gripper closing;        sealing and cutting of the bag;        
Only after the bag has been cut does the film start to unwind again.
The grippers have practically just one movement: Open-Close.
In “box motion” type functioning machines, the sealing unit functions continuously.
The grippers perform the following steps:                gripper opening;        following of the bag during the forming step;        gripper closing;        sealing;        cutting of the bag;        opening and rising.        
Throughout these operations the film does not stop, but continues to unwind.
The problem encountered with flow-pack solutions with traditional box-motion closure mainly concerns the fact that their specific design concept means that the drive organs are positioned on the package sealing and cutting carriage, which increases the mass of the operating unit thus drastically limiting the movements of the unit and slowing down the operating steps.
This all has a negative impact on the production capacity of the plant and thus on the production costs, which increase in proportion to the slowing down of the production stages.